The present invention relates to a new process for the preparation of pseudoionone, which is an intermediate of particular interest in synthesizing vitamin A.
French Patent 2,518,538 discloses the preparation of pseudoionone by treating, in a basic polar aprotic solvent, a chlorinated .beta.-ketoester of formulas Ia or Ib: ##STR3## wherein R.sub.1 represents an alkyl radical containing 1 to 4 carbon atoms, with a lithium chloride - inorganic acid - tertiary amine system at a temperature between 80.degree. C. and 160.degree. C. Formulas Ia and Ib can be obtained by reacting cupric chloride and a compound of formulas IIa and IIb: ##STR4## wherein R.sub.1 has the same definition as R.sub.1 above, in the presence of lithium chloride in a basic aprotic solvent. Compounds of Formulas of IIa and IIb are obtained by the reaction of an alkyl acetylacetate on myrcene under the conditions described in European Patent EP 44,771.
I. Minami et al., Synthesis, p. 992 (1987) and French Patent 2,526,420 teach that the oxidative decarboxylation can be performed only on .alpha.,.alpha.-disubstituted allyl .beta.-ketoesters: